Inductive coupling has become the method of choice for energy and data transmission between an external control unit and an implanted medical device, such as, for example, an infusion pump, a pacemaker or a defibrillator. To effect this communication, both the external control unit and the implantable medical devices must have an antenna so that they can communicate, usually by radio-frequency (“RF”) telemetry. The antennas are typically made of coils of one or more turns. Optimal energy and data transmission is achieved with a control unit antenna made of a coaxial cable, which shield is broken at one point to allow for RF wave radiation. However, the position of the antenna is usually fixed with respect to the control unit housing. To communicate with an implanted medical device, RF waves are emitted from the antenna. However, these RF waves can interfere with the electronics inside the control unit housing and can affect the control unit functionality.
Others have attempted to overcome these problems by using a control unit that has an antenna connected to the control unit by a cable. These control units are usually the size of a laptop computer, which is too big to be carried by the user on a daily basis. Even if the control unit were of a hand held size, the user is still required to manage two pieces simultaneously: the control unit displaying the information to manage the communication, and the antenna to be positioned on top of the implant during the interrogation.
There are control units that are of a hand held size, except the antenna in these control units is integrated in the control unit housing. The antenna is mounted about the electronics within the control unit. Thus, the RF energy emitted by the antenna is limited to minimize the interference with the electronics within the control unit. But limiting the RF energy also limits the interrogation distance and the amount of energy that can be transmitted during an energy and data transmission.
Accordingly, there is a need for a control unit for an implantable medical device that has an antenna that can communicate with the implantable medical device without interfering, or at least substantially minimizing the interference, with the electronics inside the control unit housing.